Resistive element for variable electrical resistor



Dec. 27, 1955 P. F. MOLEMAN 2,728,834

RESISTIVE ELEMENT FOR VARIABLE ELECTRICAL RESISTOR Filed Oct. 26, 1954 i INVENTOR PIETER FREERK MOLEMAN 1 AGENT United States Patent Ofiice RESISTIVE ELEMENT VARIABLE ELECTRICAL RESISTBR Pieter Freerk Moleman, Eindhoven, Netherlands, assiguor to Hartford National Bank and Trust Company, Hartford, Conm, as trustee Application October 26, 1954, Serial l o. 464,836

Claims priority, application Netherlands November 12, B53

2 Claims. (Cl. 201-63) Potentiometers and other variable electrical resistors often comprise an electrical resistive element consisting of a strip-shaped support carrying the resistive material, for example in the form of a number of wire turns made from resistive material. The contact sliding over the support for adjustment should be in eflicient electrical contact with the terminal connection of the resistive material in the end positions. For this purpose it is known to use a U-shaped metal strip covering the edge of the support, to which strip one end of the resistive material is electrically connected and which strip is secured to the support by means of a rivet passed through an aperture of the support. However, this construction suffers from a limitation in that, owing to tolerances at the registering apertures of the metal strip and the support, the former does not always rest flatly on the support, particularly on its edge. This may give rise to premature wear and sometimes to damage of the sliding contact on passing over from the resistive material to the terminal contact and furthermore the displacement of the contact onto the said strip may be impeded or even prevented by the said edge.

The present invention has for its object to provide a construction for an electrical resistive element comprising a layer of resistive material provided on a stripshaped support in which a terminal contact is formed by a U- shaped metal strip which extends over the edge of the support and is secured by means of a mechanical joint provided in an aperture of the support, by which con struction the aforesaid disadvantage of known constructions is avoided.

In accordance with the invention the metal strip is constituted by metal foil, preferably of nickel, which is tautened by means of two metal press-members inserted one at each side of a support, with the interposition of the ends of the metal foil, in the aperture of the support, the strip portions engaging each other in the aperture being electrically welded together and to the press-members.

Since the metal foil need not previously be furnished with apertures registering with the aperture of the sup- 2,728,834 il zttented Dec. 27, 1955 port, and the location of the press-members relative to the foil is only determined by the tautened foil, the latter lies flatly on the support.

in order that the invention may be readily carried into etlect, it will now be described, by way of example, with reference to the accompanying drawing, in which:

Fig. 1 shows one end of a resistive element in accordance with the invention, viewed at right angles to the plane of the support, and

Fig. 2 is a cross-sectional View on the line l -ll of Fig. l.

Resistive wire 2 is Wound on an elongated strip-shaped support 1 of insulating material, for example a material such is commercially available under the name Pertinax. A slidable contact (not shown) is arranged to pass over the turns of the wire 2 at the upper edge of the support. This support is furnished with an aperture 3 at one end, as shown in the drawing. Nickel foil 4 is provided over the edge of the support and tautened at the aperture 3 by means of two ringlets 5 and 6 one at each side of the support, which are placed on the foil and pressed into the aperture 3, the outside diameter of said ringlets being a little smaller than the diameter of the aperture 3. Where the adjacent parts of the foil 4 engage the ringlets 5 and 6 at aperture 3 they are welded together, the ringlets being similarly connected to the foil. One end of the resistive wire 2 is welded or soldered to the ringlets 6 at 7. The tautened foil strip 4 at the upper edge of the support thus forms a terminal contact for the contact slidable on said edge. Alternatively, diiferently shaped press-members, for example plates, may be used for tautening the foil 4. Preferably, however, rings are used since these permit the resistive element to be secured by means of a bolt passed through the two rings. The foil parts obstructing the passage are easily removable.

What is claimed is:

l. A resistive element for variable electrical resistors, in which the resistive material is provided on a stripshaped support and a terminal contact is constituted by a U-shaped metal strip extending over the edge of the support and secured by means of a mechanical joint fitted in an aperture of the support, characterized in that the strip consists of metal foil, preferably of nickel, which is tautened by means of two metal press-members inserted one at each side or" a support, with the interposition of the ends of the metal foil, in the aperture of the support, the strip portions engaging each other in the aperture being electrically welded together and to the pressmembers.

2. A resistive element as claimed in claim 1, characterized in that the press-members are rings.

No references cited. 

